No sensation during sex.

Patient: I am a male 51. Separated for 2 years not having sex for 3 years. I just met a lady and we are having sex. My problem is I have no sensation. She will have 5 to 8 orgasms and I will have none. Erection remains throughout.No problem with erection or sexual attraction. If I masturbate with little visual stimulation I get a very high intensity when ejaculating. Everything shivers.Why do I get no sensation with my partner. I will sometimes ejaculate but most of the time not. Why? It is embarrassing.